Hard to say from the pictures. How mechanically inclined are you?
Changing the fluid on your tranny, you have to put the rear up on jackstands and make the bottom of the tranny LEVEL. Plus a few other things. It's a lot more involved than the tranny's of old (and quite a bit more expensive for parts/fluid overall). Best might be to go to Y/T and watch some ZF tranny fluid/filter change videos.
If it's the O-ring for the lever, that would probably involve removing the valve body. But I haven't done it on that transmission. Hopefully someone else will chime in. Then again, it could be something else, or even a leak off the engine. See if there are any videos on ZF tranny leaks (not just on Rams). ZF transmissions are used in a lot of vehicles. Probably a lot easier to take it to the dealer.